The present invention relates to a suction device for easily handling a semiconductor wafer which is required to be handled very carefully.
Conventionally, a semiconductor wafer is handled while being pinched on the front and back sides thereof with tweezers. However, the handling of the semiconductor wafer with the tweezers has problems mentioned below.
Namely, when the semiconductor wafer is pinched with the tweezers, stress is concentrated to the portion of the wafer which is in contact with the tweezers.
Since the semiconductor wafer such as a single crystal of silicon and a single crystal of gallium arsenide (GaAs) is a damageable material and has a very small thickness, the wafer is likely to crack from its portion in contact with the tips of the tweezers.
When the semiconductor wafer is pinched at about the center of gravity thereof, that is, at about the center of a flat-shaped wafer, with the tweezers in order to reduce the likelihood of cracking or damaging of the wafer, the processed region of the wafer is likely to be damaged by the tips of the tweezers.
Since the stress against the semiconductor wafer concentrates to its very small portion where the tweezers contacts the wafer in the pinching of the wafer with the tweezers, it is necessary to be very careful in handling the wafer. However, the wafer is still likely damaged in the handling thereof with the tweezers even if the wafer is very carefully handled.
If the tips of the tweezers are coated with a soft material for protecting the semiconductor wafer from damage, the tips of the tweezers are made so thick and round as to deteriorate the operating property of the tweezers for picking up the semiconductor wafer which is, for example, put on a flat rest.
For a Si chip, vacuum tweezers are conventionally used. FIG. 1 shows such a conventional vacuum tweezers. A nozzle 40 is attached to the tip of a grip 42. The air in the inside of the grip is exhausted through a hose 43 connected to a vacuum pump (not shown). When the nozzle 40 is made to contact with a chip and a hole 41 is closed by an operator's finger, the chip is absorbed to the nozzle. When the finger is released from the hole, the chip is separated from the nozzle.
However, since the nozzle of the conventional vacuum tweezers has only one through hole, a comparatively large stress is applied to the chip at its small portion where the vacuum tweezers contact with the chip. Although the conventional vacuum tweezers are originally intended to be used for the handling of the chip, they are applicable for a Si wafer in some cases. Since a Si wafer is less brittle and generally thicker than a GaAs wafer, the conventional vacuum tweezers are applicable for the Si wafer. However, they have not been used for a GaAs wafer.